On 2019-12-31 15:44, Stanley Chu wrote:
Hi Can,
On Tue, 2019-12-31 at 12:22 +0800, Stanley Chu wrote:
Hi Can,
> Hi Stanley,
>
> I see skipping ufshcd_set_ufs_dev_active() in ufshcd_probe_hba()
> if it is called from ufshcd_resume() path is the purpose here.
>
> If so, then ufshcd_set_dev_pwr_mode() would be called, meaning
> SSU command will be sent. Why is this SSU command needed to be
> sent after a full host reset and restore? Is ufshcd_probe_hba()
> not enough to make UFS device fully functional?
After resume (for both runtime resume and system resume), device power
mode shall be back to "Active" to service incoming requests.
I see two cases need device power mode transition during resume flow
1. Device Power Mode = Sleep
2. Device Power Mode = PowerDown
For 1, ufshcd_probe_hba() is not invoked during resume flow,
hba->curr_dev_pwr_mode = SLEEP, thus ufshcd_resume() can invoke
ufshcd_set_dev_pwr_mode() to change device power mode.
For 2, ufshcd_probe_hba() is invoked during resume flow, before this
fix, hba->curr_dev_pwr_mode will be set to ACTIVE (note that only this
flag is set as ACTIVE, but device may be still in PowerDown state if
device power is not fully shutdown or device HW reset is not executed
before resume), in the end, ufshcd_resume() will not invoke
ufshcd_set_dev_pwr_mode() to send SSU command to make device change
back
to Active power mode.
But if device is fully reset before resume (not by current mainstream
driver), device can be already in "Active" power mode after power on
again during resume flow. In this case, it is OK to set
hba->curr_dev_pwr_mode as ACTIVE in ufshcd_probe_hba() and SSU command
is not necessary.
Thanks,
Stanley
I think currently the assumption in ufshcd_probe_hba() that "device
shall be already in Active power mode" makes sense because many device
commands will be sent to device in ufshcd_probe_hba() but device is not
promised to handle those commands in PowerDown power mode according to
UFS spec.
So, maybe always ensuring device being Active power mode before leaving
ufshcd_probe_hba() is more reasonable. If so, I will drop this patch
first.
Thanks so much for your reviews.
Happy new year!
Thanks,
Stanley
Hi Stanley,
I missed this mail before I hit send. In current code, as per my
understanding,
UFS device's power state should be Active after ufshcd_link_startup()
returns.
If I am wrong, please feel free to correct me.
Due to you are almost trying to revert commit 7caf489b99a42a, I am just
wondering
if you encounter failure/error caused by it.
Happy new year to you too!
Thanks,
Can Guo
